The purpose of this study is to obtain normal human lipoproteins for studies involving alterations in the physical and chemical properties of the lipoproteins and their interactions with cells. The chemistry of oxidation of low density and high density lipoproteins is studied, as well as the toxic effects of the oxidized lipoproteins on porcine vascular smooth muscle cells. Uptake of aggregated low density lipoproteins in porcine vascular smooth muscle cells is studied.